Yes RichardV6, I believe they are called crush tubes. They determine the distance between the remote and the gearbox faces. So, as you say, tighten up until you feel it "bottoming out". If the crush tubes are long you may need an extra plane bush in addition to the lipped one before you feel the resistance on tightening the bolt. Some Loctite or similar might be a good idea as there are no lock washers used on these bolts.
